Contact device for electric switches



Feb. 13, 1968 SHINICHI MURAKAMI 3,369,097

CONTACT DEVICE FOR ELECTRIC SWITCHES Filed March 14, 1967 FIG. I

cl A J71 United States Patent 3,369,097 CONTACT DEVICE FOR ELECTRIC SWITCHES Shinichi Murakami, Hamamatsu-shi, Japan, assignor to Nippon Gakki Seizo Kabushiki Kaisha, Hamamatsu-shi, Japan Filed Mar. 14, 1967, Ser. No. 622,973 Claims priority, application Japan, Apr. 30, 1966 (utility model), 41/ 40,189 4 Claims. (Cl. 200166) ABSTRACT OF THE DISCLOSURE Electroconductive elastic contacts are held in position by a plurality of spaced open slots provided along one edge of a mounting board of electric insulating material. Each of the open slots comprises a linear portion and a circular enlarged portion at the inner end of the linear portion, the diameter of the enlarged portion being larger than the width of the linear portion but slightly smaller than the diameter of the elastic contact, thus firmly securing it in position.

This invention relates to elastic contacts such as electroconductive rubber contacts for electric switches.

Metal contacts, which do not have rubber elasticity, in electric switches are generally secured to supporting means by clamping the contacts between plates or by threading them through perforations drilled through supporting means. However, these securing means require considerable time in assembling and are not completely satisfactory. On the other hand, it is highly desirable that so-called elastic contacts, for example, contacts covered with a synthetic resin such as electroconductive rubber or electroconductive vinylon, be readily secured in a simple manner at definite positions without utilizing screws or other fixing elements irrespective of the eccentricity of their core conductors.

It is therefore an object of this invention to provide an improved securing means for electroconductive elastic contacts of a switch.

Another object of this invention is to provide a novel securing means for electroconductive elastic contacts wherein the contacts can be quickly inserted and firmly held in position.

Briefly stated, in accordance with this invention a series of spaced contact-receiving open slots are provided along an edge of a mounting board of electric insulating material. Each of the slots comprises a relatively narrow linear portion and an enlarged portion at the inner end of the linear portion, said enlarged portion being adapted to receive an elastic contact and having a diameter slightly smaller than that of the elastic contact. This arrangement permits quick insertion and removal of elastic contacts and yet prevents accidental removal thereof.

The invention can be more fully understood from the following detailed description with respect to a preferred embodiment of the invention when taken with the accompanying drawing in which:

FIG. 1 is a front elevation of an example of a contact device embodying this invention;

FIG. 2 is a sectional view of the contact device taken along a line IIII in FIG. 1; and

FIG. 3 is a sectional view to illustrate the relative posi- 3,369,097 Patented Feb. 13,, 1968 tion of the contact device and the other elements of an electric switch.

Referring now to the accompanying drawing, a plurality of elastic contacts 1 and 1a are supported by a pair of mounting boards 2 of electric insulating material. A plurality of spaced key-hole shaped open slots 3 are provided along one edge of each mounting board 2. Each slot 3 is an open slot comprising a linear portion 3a having a width narrower than the diameter of contact 1 or 1a and a circular enlarged portion 3b at the inner end of the linear portion 3a and having a diameter larger than the width of the linear portion but slightly smaller than the diameter of contact 1 or 1a. As shown in FIGS. 2 and 3, eachof contacts 1 and 1a is inserted into the enlarged portion 3b through the linear portion 3a of the open slot 3. As the width of the linear portion 3a is smaller than the outer diameter of the elastic contact, once .the contact is pushed into the enlarged portion accidental removal of the contact is prevented.

FIG. 3 illustrates the relation between electroconductive elastic contacts 1 and 1a and other components of a switch. As shown, a portion of FIG. 3, between a pair of adjacent contacts 1 and 1a (upper in FIG. 3) and above each of contacts 1 (lower three), there are respectively disposed movable wire contacts 4 which are passed through an actuator 5. The actuator 5 is guided by perforations 8 and 9 through spaced horizontal supporting plates 6 and 7 to be movable in the vertical direction. Thus, when the actuator 5 is depressed, each movable wire contact 4 is caused to engage one of the elastic contacts 1 to establish an electric circuit. Electroconductive elastic contact designated by reference numeral 1a is a counter contact (normally closed contact).

Thus, according to this invention, it is possible to readily insert elastic contacts in position, and yet accidental removal thereof is precluded as the elastic contacts are retained in enlarged sections 3b by slight compressive force centripetally acting upon the periphery thereof. Further, as the elastic contacts are supported at their outer surface and not at core members, the contacts are set at correct position with respect to corresponding wire contacts, irrespective of the eccentricity of the core conductors with respect to elastic electroconductive sleeves. Thus,

' when used for key switches in electrical musical instrufrom the scope of the invention as defined in the appended claims.

What I claim is:

1. In a contact device for an electric switch, comprising a plurality of electroconductive elastic contacts and at least one mounting board made of an electrically insulating material and holding said elastic contacts in position; the improvement residing in that said mounting board has a plurality of spaced open slots along one edge thereof, each of said slots including a linear portion and an enlarged portion at the inner end of said linear portion, said enlarged portion being adapted to receive a respective one of said elastic contacts.

2. The contact device according to claim 1 wherein each one of said elastic contacts comprises a core conductor and an electroconductive rubber sleeve covering said core conductor.

3. The contact device according to claim 1 wherein the diameter of said enlarged portion is slightly smaller than the outer diameter of the elastic contact.

4. The contact device according to claim 1 wherein a movable contact is disposed between each pair of adjacent elastic contacts, and an actuator is provided to switch said movable contact between said pair of adjacent elastic contacts.

4' References Cited UNITED STATES PATENTS 2,931,877 4/1960 Henley 200l66 5 ROBERT K. SCHAEFER, Primary Examiner.

H. O. JONES, Assistant Examiner. 

